1. The Integumentary System
Lab Exercise 7
The Integumentary System
Portland Community College
BI 231

2. Skin Or Cutaneous membrane is an organ.
(an organ is a structure that contains two or more of the primary tissue types)
Embedded within the skin are various accessory structures the combination of both is called the integumentary system

3. Skin Epidermis: Superficial layer
Made of stratified squamous keratinized epithelium
4-5 Layers
Dermis: Underlying connective tissue layer
2 Layers
Hypodermis: Not part of the skin, it is deep to the dermis
Primarily adipose tissue

4. Layers of the epidermis
Stratum basale: single row of cells
Adjacent to the dermis and attached by the basement membrane.
Constantly dividing and pushing up layers
Melanocytes with melanin protects the skin from UV radiation

5. Layers of the Epidermis
Stratum spinosum: several cell layers superficial to stratum basale.
Cells also dividing
Cells contain bundles of intermediate filaments made of pre-keratin
Cells appear star-shaped because the cell membrane pulls away from the other cells, except in areas where desmosomes are.

6. Layers of the Epidermis
Stratum granulosum:
The upper part of this layer has cells that are beginning to die
Lamellated granules contain a waterproofing glycolipid that is secreted into the extracellular space
Keratohyaline granules combine with intermediate filaments to form keratin fibrils

7. Layers of the Epidermis
Stratum lucidum: Thin translucent layer of dead keratinocytes
Found only in thick skin

8. Layers of the Epidermis
Stratum corneum: Outermost layer
20-30 cell layers thick
Cells are dead and flattened
Full of keratin
Constantly being rubbed off

10. Epidermis cell phases
Deepest layer (basale) goes through rapid division.
Middle layers undergo a process of producing precursor molecules that lead to waterproofing of the cells.
The final phase is the completion of the waterproofing process. Cells eventually die, providing a tough barrier

11. Dermis The dermis is the connective tissue layer under the epidermis.
Composed of primarily of fibers:
Irregularly arranged collagen fibers make up the majority and provide strength and flexibility to skin
Lesser numbers of elastic fibers which provided elasticity to the skin
There are also reticular fibers found in the dermis
blood vessels, nerves, sensory receptors, hair follicles and glands.

12. Dermis Papillary Layer: Superficial dermal region
Areolar connective tissue
Contains capillaries, lymphatics and sensory neurons
Dermal Papillae: the fingerlike projections from the superior surface
Epidermal ridge: The epidermal layer that dips down into the dermal papillae
Create fingerprints

13. Epidermis
Epidermal ridge
Papillary Layer
Dermal Papillae
Reticular Layer

14. Finger Prints
Epidermal
Ridge

15. Dermis Reticular Layer: Deepest skin layer
Dense irregular connective tissue
Contains the arteries, veins, sweat and sebaceous glands
Cleavage lines: the deep creases (like in the palm) where collagen and elastic fibers are arranged in parallel bundles.

16. Hypodermis Subcutaneous layer that is not part of the skin
Beneath the dermis layer
Composed of adipose and areolar connective tissue
Highly vascular
Hypodermis

17. Cells of the Epidermis Keratinocytes: The main cells of the epidermis
Produce keratin, water proof protein
As new cells form, they push the older cells toward the surface, where they gradually accumulate keratin and eventually die
Melanocytes: Spidery black cells
In stratum basale
Produce melanin, the pigment that protects skin from UV damage

18. Cells of the Epidermis

19. Meissner’s (Tactile) Corpuscle
Located in the dermal papillae
Receptor for light touch

20. Merkel Cells
Merkel Cells: At the junction of the sensory nerve endings
In upper dermis and ll
lower epidermis
Light touch (like fly
walking over cheek)

21. Pacinian (Lamellated) Corpuscle
Lie deep in the dermis
Respond only when deep pressure is first applied
Monitor high frequency vibrations

22. Other skin receptors
Warm and cool receptors: When you are at comportable temperature both of these are firing
If you increase or decrease the skin temperature beyond the range of these receptors, pain receptors are stimulated.
Pain receptors are naked nerve endings in the dermis that respond to numerous environmental stimuli.

23. Integumentary Glands Sudoriferous (sweat) glands
Lactiferous (milk) glands
Sebaceous (oil) glands
Ceruminous (earwax) glands

24. Eccrine (Merocrine) Sweat Glands
Eccrine sweat glands
Ducts open directly on the surface of the epidermis
Produce normal body perspiration.
Reduces body temperature by evaporative cooling

25. Apocrine Sweat Glands
Apocrine glands: secrete a water and a higher concentration of organic acids than eccrine glands that bacteria can use for nutrients (creates body odor)
Found in the armpits, around nipples and in the pubic region
Secrete products into hair follicles or directly onto the surface.
Begin functioning at puberty

26. Apocrine Sweat Glands Red arrow - Apocrine Sweat Glands
Green arrow - Hair follicle

27. Sebaceous Glands Sebaceous glands Produce oily substance called sebum
Helps waterproof the skin
Acne: infection of the sebaceous gland

28. Hair Keratinized cells produced in
Hair follicles: tubular compartments that contain hair(projections of the epidermis into dermis)

29. Hair Bulb: deepest portion of the hair follicle
Bulb contains the hair matrix which contains actively dividing cells
The actively dividing cells give rise to the hair root.
As hair root approaches the surface of the skin it becomes the hair shaft.
Hard Keratin covers the hair

30. Hair Histology

31. Arrector Pili Muscle
Arrector pili muscle: Smooth muscle that pull hair upright during fright or cold (goose bumps)

32. Hair Determinate hair grows to a specific length and then stops
Found in axilla, groin, eyelashes and eyebrows.
Indeterminate hair grows without regard to length.
Found on scalp and beards

33. Hair
Medulla central portion of the hair which is enclosed by an outer cortex.
The cortex may contain pigments which give the hair its color (melanin)
The cuticle is superficial to the cortex

34. Fingernails Scale like modification of the epidermis
Free edge: part that grows away from the finger
Body: The nail
Root: Embedded in skin and sticks to the nail bed
Nail Bed: Extension of the stratum basale beneath the nail
Nail Matrix: Proximal part of the nail bed responsible for nail growth
Lunula: white crescent area; Most active growth region of nail matrix

35. Fingernail Structures

36. Muscle Tissue
Like epithelial tissue, muscular tissue is a cellular tissue with the tissue having mostly cells and little matrix
There are three types of muscle: skeletal, cardiac and smooth

37. Skeletal Muscle
Cells called fibers
Striated
Voluntary
Multinucleate

38. Sarcomere

39. Cardiac Muscle Striated but striations are much less obvious.
Cardiac muscle cells are called myocytes.
Branched
Involuntary
Intercalated discs, which facilitate the transmission of the electrical impulses in the heart

40. Smooth Muscle Nonstriated Involuntary
Cells of smooth muscle are spindle-shaped
Found in intestine where it propels food along by a process known as peristalsis and segmentation

41. The End
The End